17. The girl lost her balance and fell off the balance beam.

　　小女孩失去了平衡，从平衡木上摔了下来。

　　18. She rolled the socks into a ball.

　　她把袜子卷成一团。

　　19. How did you enjoy the ball?

　　你们在舞会上玩得高兴吗?

　　20. A band of robbers held up the train.

　　一群强盗抢劫了火车。

　　21. The town stands on the left bank of the river.

　　城镇位于河的左岸。

　　22. He has a large deposit in the bank.

　　他在银行有大笔存款。

　　23. The organ has two banks of keys.

　　那架风琴有两排键盘。

　　24. Clouds are banking up.

　　云层正在堆积。